Keyboard musical instruments generally refer to pianos, digital pianos, and so on. For a traditional piano, each piano key is connected to a hammer covered with felt. When a player presses a piano key, the hammer strikes the string, causing it to vibrate to produce the sound. In this case, the sound is produced using mechanical devices. The digital piano is evolved from the traditional piano. When a piano key is pressed, the corresponding stored sound source is sent to the amplifier after being processed and finally arrives at the speaker to produce the sound. In this case, the sound is produced by electronic devices.
Since the traditional piano makes a sound through mechanical devices, each piano key on the keyboard has a fixed frequency, i.e., a fixed pitch. Pitch is the quality that allows people to classify a sound as relatively high or low. Pitch is a basic feature of the sound and it is determined by the frequency of sound wave vibrations. The higher the frequency, the higher the pitch, and vice versa. To adjust the pitch of a piano key for the traditional piano, professional piano tuners need to adjust the mechanical devices accordingly. For digital pianos, since the sound is produced by electronic devices, the sound source decides what the sound is like as long as the sound source is within the passband of the speaker. Therefore, the pitch of a piano key is adjustable for digital pianos.
A piano keyboard has 52 white keys and 36 black keys, totaling to 88 keys, which include seven octaves plus a minor third (from A0 to C8). Each octave has 12 keys including 7 white keys and 5 black keys, which correspond to the twelve notes of a musical scale according to the twelve-tone equal temperament. For the middle octave, the seven white keys are named “C, D, E, F, G, A, B” and the five black keys are named “C#, D#, F#, G#, A#”. Since the frequency ratio of two notes an octave apart is 2:1, the frequency ratio of two adjacent notes in an octave is 2 1/12, i.e., each octave is divided into 12 parts, all of which are equal on a logarithmic scale. Based on this principle, the frequency range of the piano keyboard extends from 27.5 Hz to 4186 Hz and the pitch of a piano key is derived by multiplying (ascending) that of the previous key by 2 1/12. Then the strings are designed to produce sound with the frequencies of the corresponding piano keys. In the numbered musical notation, an octave has only seven music notes with the notation of “1, 2, 3, 4, 5, 6, 7” and their solfège syllables are “do, re, mi, fa, sol, la, si”, respectively. Therefore, the relationship between the twelve piano keys in an octave of the piano keyboard and the seven solfège syllables is not fixed, i.e., a piano key does not have a fixed solfège syllable. Which piano key corresponds to “do” (the digit “1”) is determined by the key of a piece. As long as the key is chosen for a piece, there is a one-to-one relationship between the twelve piano keys in an octave of the piano keyboard and the seven solfège syllables. For example, if the key is the C major scale, the key signature is defined as “1=C” and the seven notes of the C major scale “C, D, E, F, G, A, B” correspond to “do, re, mi, fa, sol, la, si”, respectively. When “1=F#”, the key is the F# major scale and the seven notes of the F# major scale “F#, G#, A#, B, C#, D#, F” correspond to “do, re, mi, fa, sol, la, si”, respectively. Obviously, the solfège syllable of a piano key is not fixed. Since any piano key in an octave of the piano keyboard can be “do”, there are twelve possible keys for a piece.
A digital piano is an electronic device, where the frequency of the sound is adjustable. So the key can be changed easily and this is referred to as “key change with one button”. When the key is changed, a piano key still corresponds to the same solfège syllable, which is one of the main features of digital pianos. Moreover, digital pianos have multiple timbres and can imitate the sound of many instruments. A digital piano has at least dozens of and sometimes even hundreds of timbres. The richness of timbres is another main feature of digital pianos. To choose a timbre, we just need to press the corresponding button in the timbre control section on the front panel. The timbres of a digital piano include two categories, common timbres and special timbres. The common timbres are used to imitate the sound of common instruments, while the special timbres are for imitating the natural sounds and imagined timbres. Temperament in music includes the twelve-tone equal temperament, the temperament based on the five-element theory, just intonation, etc. For different temperaments, the frequency ratio of two adjacent solfège syllables is different. Since digital pianos can adjust the frequency of the sound, they can support multiple temperaments. However, since digital pianos are originally invented to imitate traditional pianos, they are basically designed based on traditional pianos and only have twelve fixed keys. The function of “key change with one button” is seldom used. Moreover, after the key, timbre and temperament are chosen, the sound of a piano key is fixed and the players are given few opportunities to improvise, which leads to poor interaction. If the players can slightly adjust the frequency of a piano key during playing, just like vibrato in string instruments, then they will have more room for creation.
The numbered musical notation and the staff notation are two most popular musical notation systems. The numbered musical notation is a simple notation system, where numbers 1 to 7 are used to represent the musical notes and are respectively called “do, re, mi, fa, sol, la, si”. The number “0” represents the musical rest. In the numbered musical notation, solfège syllables are octave-repeating. For example, high “do” is an octave higher than “do” (“1”) and it begins a cyclic repetition with a higher pitch. The numbers in the numbered musical notation are referred to as solfège digits in this invention. The numbered musical notation can facilitate recording musical notes by hand and sight singing. However, it cannot describe some elements of a piece, such as dynamics, etc. The staff notation is currently the most common musical notation method in the world. It is a set of 5 horizontal lines and 4 spaces that each represent a different musical pitch. Compared with the numbered musical notation, it is much easier to visualize the essential musical elements, such as pitch, duration, time signature, tempo, dynamics, clef, etc., on the staff notation. However, the staff notation is not designed based on solfège syllables and is not suitable for sight singing.
In summary, for a traditional piano, a piano key has a fixed pitch and does not correspond to a fixed solfège syllable; for a digital piano, a piano key can have a fixed solfège syllable and its pitch is adjustable, but it is still impossible to play in an arbitrary key and the frequency of a piano key cannot be slightly adjusted during playing. For musical notation systems, the numbered musical notation is not suitable for playing and the staff notation cannot facilitate sight singing. If the advantages of these two notation systems can be combined and the elements of playing are added to the numbered musical notation, then reading music notation will become much easier and in the meantime all the musical elements are represented precisely. Furthermore, if a piano based on a keyboard with fixed solfège is provided, then it will be no longer difficult to learn to play the piano.